why not `remaining`?

`timeout.duration` is akka.test.default-timeout = 5s (no dilation)
`remaining` without `within` is akka.test.single-expect-default =  = 3s (dilated)

I'm not sure there is still a mix of this timeout.duration and await remaining, but I guess it would be easy to introduce that mix again, which would be very confusing, especially due to the dilation